intrusive_ptr
class templateintrusive_ptr
class template
Introduction
Synopsis
Members
Free Functions
The intrusive_ptr class template stores a pointer to an object with an embedded reference count. Every new intrusive_ptr instance increments the reference count by using an unqualified call to the function intrusive_ptr_add_ref, passing it the pointer as an argument. Similarly, when an intrusive_ptr is destroyed, it calls intrusive_ptr_release; this function is responsible for destroying the object when its reference count drops to zero. The user is expected to provide suitable definitions of these two functions. On compilers that support argument-dependent lookup, intrusive_ptr_add_ref and intrusive_ptr_release should be defined in the namespace that corresponds to their parameter; otherwise, the definitions need to go in namespace boost.
The class template is parameterized on T, the type of the object pointed to. intrusive_ptr<T> can be implicitly converted to intrusive_ptr<U> whenever T* can be implicitly converted to U*.
The main reasons to use intrusive_ptr are:
As a general rule, if it isn't obvious whether intrusive_ptr better fits your needs than shared_ptr, try a shared_ptr-based design first.
namespace boost {
template<class T> class intrusive_ptr {
public:
typedef T element_type;
intrusive_ptr(); // never throws
intrusive_ptr(T * p, bool add_ref = true);
intrusive_ptr(intrusive_ptr const & r);
template<class Y> intrusive_ptr(intrusive_ptr<Y> const & r);
~intrusive_ptr();
intrusive_ptr & operator=(intrusive_ptr const & r);
template<class Y> intrusive_ptr & operator=(intrusive_ptr<Y> const & r);
template<class Y> intrusive_ptr & operator=(T * r);
T & operator*() const; // never throws
T * operator->() const; // never throws
T * get() const; // never throws
operator unspecified-bool-type() const; // never throws
void swap(intrusive_ptr & b); // never throws
};
template<class T, class U>
bool operator==(intrusive_ptr<T> const & a, intrusive_ptr<U> const & b); // never throws
template<class T, class U>
bool operator!=(intrusive_ptr<T> const & a, intrusive_ptr<U> const & b); // never throws
template<class T>
bool operator==(intrusive_ptr<T> const & a, T * b); // never throws
template<class T>
bool operator!=(intrusive_ptr<T> const & a, T * b); // never throws
template<class T>
bool operator==(T * a, intrusive_ptr<T> const & b); // never throws
template<class T>
bool operator!=(T * a, intrusive_ptr<T> const & b); // never throws
template<class T, class U>
bool operator<(intrusive_ptr<T> const & a, intrusive_ptr<U> const & b); // never throws
template<class T> void swap(intrusive_ptr<T> & a, intrusive_ptr<T> & b); // never throws
template<class T> T * get_pointer(intrusive_ptr<T> const & p); // never throws
template<class T, class U>
intrusive_ptr<T> static_pointer_cast(intrusive_ptr<U> const & r); // never throws
template<class T, class U>
intrusive_ptr<T> const_pointer_cast(intrusive_ptr<U> const & r); // never throws
template<class T, class U>
intrusive_ptr<T> dynamic_pointer_cast(intrusive_ptr<U> const & r); // never throws
template<class E, class T, class Y>
std::basic_ostream<E, T> & operator<< (std::basic_ostream<E, T> & os, intrusive_ptr<Y> const & p);
}
typedef T element_type;
Provides the type of the template parameter T.
intrusive_ptr(); // never throws
Postconditions:
get() == 0.Throws: nothing.
intrusive_ptr(T * p, bool add_ref = true);
Effects:
if(p != 0 && add_ref) intrusive_ptr_add_ref(p);.Postconditions:
get() == p.
intrusive_ptr(intrusive_ptr const & r); // never throws template<class Y> intrusive_ptr(intrusive_ptr<Y> const & r); // never throws
Effects:
if(r.get() != 0) intrusive_ptr_add_ref(r.get());.Postconditions:
get() == r.get().
~intrusive_ptr();
Effects:
if(get() != 0) intrusive_ptr_release(get());.
intrusive_ptr & operator=(intrusive_ptr const & r); // never throws template<class Y> intrusive_ptr & operator=(intrusive_ptr<Y> const & r); // never throws intrusive_ptr & operator=(T * r);
Effects: Equivalent to
intrusive_ptr(r).swap(*this).Returns:
*this.
T & operator*() const; // never throws
Requirements:
get() != 0.Returns:
*get().Throws: nothing.
T * operator->() const; // never throws
Requirements:
get() != 0.Returns:
get().Throws: nothing.
T * get() const; // never throws
Returns: the stored pointer.
Throws: nothing.
operator unspecified-bool-type () const; // never throws
Returns: an unspecified value that, when used in boolean contexts, is equivalent to
get() != 0.Throws: nothing.
Notes: This conversion operator allows intrusive_ptr objects to be used in boolean contexts, like
if (p && p->valid()) {}. The actual target type is typically a pointer to a member function, avoiding many of the implicit conversion pitfalls.
void swap(intrusive_ptr & b); // never throws
Effects: Exchanges the contents of the two smart pointers.
Throws: nothing.
template<class T, class U> bool operator==(intrusive_ptr<T> const & a, intrusive_ptr<U> const & b); // never throws
Returns:
a.get() == b.get().Throws: nothing.
template<class T, class U> bool operator!=(intrusive_ptr<T> const & a, intrusive_ptr<U> const & b); // never throws
Returns:
a.get() != b.get().Throws: nothing.
template<class T> bool operator==(intrusive_ptr<T> const & a, T * b); // never throws
Returns:
a.get() == b.Throws: nothing.
template<class T> bool operator!=(intrusive_ptr<T> const & a, T * b); // never throws
Returns:
a.get() != b.Throws: nothing.
template<class T> bool operator==(T * a, intrusive_ptr<T> const & b); // never throws
Returns:
a == b.get().Throws: nothing.
template<class T> bool operator!=(T * a, intrusive_ptr<T> const & b); // never throws
Returns:
a != b.get().Throws: nothing.
template<class T, class U> bool operator<(intrusive_ptr<T> const & a, intrusive_ptr<U> const & b); // never throws
Returns:
std::less<T *>()(a.get(), b.get()).Throws: nothing.
Notes: Allows intrusive_ptr objects to be used as keys in associative containers.
template<class T> void swap(intrusive_ptr<T> & a, intrusive_ptr<T> & b); // never throws
Effects: Equivalent to
a.swap(b).Throws: nothing.
Notes: Matches the interface of std::swap. Provided as an aid to generic programming.
template<class T> T * get_pointer(intrusive_ptr<T> const & p); // never throws
Returns:
p.get().Throws: nothing.
Notes: Provided as an aid to generic programming. Used by mem_fn.
template<class T, class U> intrusive_ptr<T> static_pointer_cast(intrusive_ptr<U> const & r); // never throws
Returns:
intrusive_ptr<T>(static_cast<T*>(r.get())).Throws: nothing.
template<class T, class U> intrusive_ptr<T> const_pointer_cast(intrusive_ptr<U> const & r); // never throws
Returns:
intrusive_ptr<T>(const_cast<T*>(r.get())).Throws: nothing.
template<class T, class U> intrusive_ptr<T> dynamic_pointer_cast(intrusive_ptr<U> const & r);
Returns:
intrusive_ptr<T>(dynamic_cast<T*>(r.get())).Throws: nothing.
template<class E, class T, class Y>
std::basic_ostream<E, T> & operator<< (std::basic_ostream<E, T> & os, intrusive_ptr<Y> const & p);
Effects:
os << p.get();.Returns:
os.
$Date: 2004/10/05 15:45:50 $
Copyright © 2003 Peter Dimov. Permission to copy, use, modify, sell and distribute this document is granted provided this copyright notice appears in all copies. This document is provided "as is" without express or implied warranty, and with no claim as to its suitability for any purpose.